Electronic circuit



June 18, 1957 Filed April 27, 1954 Number Va d wmber in Space J. J.LENTZ 2,796,521

ELECTRONIC CIRCUIT 2 Sheets-Sheet 2 FIG. 2

INVENTOR JOHN J. LE/VTZ ATTORNEY United States Patent Business MachinesCorporation, New York, N. Y., a corporation of New York ApplicationApril 27, 1954, Serial No. 425,993

6 Claims. (Cl. 250-27) The invention relates to a novel storage deviceand more particularly to an electronic regeneration device that willremember indefinitely.

The principle object of the present invention is to provide an improvedstorage device that is relatively compact, inexpensive to construct andhighly stable in operation.

Another object of the present invention is to provide a storage devicethat will accept data for storage at any instant in time and have saidstored data available at subsequent periodic intervals of time.

An additional object of the present invention is to provide a storagedevice, which upon receipt of data to be stored, will inherently resetor discard any data stored in said device and accept and store thepresently submitted data.

A still further object of the present invention is to provide a storageunit capable of accepting data expressed in widely varying wave formsand furnishing said data at a subsequent period in time in a morereadily usable wave form.

Yet another object of the present invention is the provision of astorage device finding application as a delay circuit or a combinationdelay circuit storage device.

A still further object of the present invention is the provision ofstorage device that will directly and simply store decimal values.

A yet further object of the present invention is a delay circuit whereinthe delay time is substantially independent of tube characteristics.That is the mathematical expression for the time delay of the delaycircuit is a function only of the second and higher orders of the tubeconstants.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

The novel storage device herein disclosed is for use in storing for anindefinite period a number or data represented as a voltage impulseoccurring at a preselected time relative to a standard time baseinterval. In so representing a number, a continuously repeated standardtime base interval of predetermined length is established and is dividedinto ten equal divisions corresponding to the numbers 0 through 9. Animpulse at any one of these divisions in any time base intervalrepresents the corresponding number.

An impulse appears at the output of the novel storage circuit at a timecorresponding to the particular number in each time base intervalfollowing the original introduction of the number to the circuit. Thisoutput impulse continues thus to appear periodically until a new numberis introduced.

'More specifically, the novel storage device includes a multi-electrodetube having two control grids it being necessary that a positive voltagebe impressed simultaneously on both said control grids to cause anodecurrent. Synchronizing means is provided to supply synchronous positiveimpulses to one of said control grids of the multielectrode tube; asynchronizing impulse occurring at each time division of each baseinterval. The'other control grid of the multi-electrode tube isconnected to an RC timing circuit at a point in the RC circuit having asteady state voltage of positive value with respect to the cathode ofthe multi-electrode tube. A clamping circuit is provided which isefiective to clamp the grid connected to the RC circuit, and one side ofthe capacitor of the RC circuit, momentarily to a negative line inresponse to an impulse to be stored or the regeneration of a storedimpulse. Following the clamping action of the clamping circuit, the timeof return of said other control grid to a positive voltage depends uponthe time constant of the RC circuit. This RC circuit is designed tocause said other control grid of the multi-electrode tube to becomepositive approximately one-half of a time division ahead of the time inthe next time base interval corresponding to the original impulse. Thenext synchronous pulse applied to said one of said control grids of saidmultielectrode tube results in an output pulse and the recycling of thestorage device.

The above discussion will be more clear from the detailed descriptionthat follows. In addition, however, it is well to appreciate at thistime, that the interval between the initiation and ending of thedischarge period of the capacitor of the RC circuit is accuratelycontrolled.

In the drawings:

Fig. 1 is a schematic circuit diagram of the novel storage device (ordelay circuit) in accordance with a preferred embodiment of the presentinvention; and

Fig. 2 is a graphical representation to a common time base of theapproximate voltage wave forms which exist at the designated points inthe circuit of Fig. l.

'The storage unit as shown in Fig. 1 includes a main control tube 11having an anode, a cathode and at least two control grids and a screengrid. A type 6BE6 has been found satisfactory for use as the controltube. The anode of the control tube 11 is connected through a resistor12 to a +400 volts supply line 13. The cathode of the control tube 11 isconnected by line 14 to a regulator unit 15 which serves to maintain thecathode constantly at a voltage approximately one-half of the value ofthe voltage of supply line 13. (From the detailed discussion thatfollows it will be appreciated that the important feature is merely tokeep the cathode of tube 11 at a potential that is a fixed percentage ofthe potential of supply line 13). r

The first control grid llcgl of the control tube-11 is connected througha pair of series connected resistors 16 and 17 to the =+400 volts supplyline 13. It is also connected through a timing capacitor 18 to the anodeof the control tube 11. The first control grid 11cg1 is also connectedthrough clamping tube 20 to grounded line 19. The clamping tube 20 maybe a triode vacuum tube, such as one-half of a type 12AT7.

The second control grid 11cg2 of the control tube 11 is connected to asuitable source of synchronizing voltage impulses designated as numberimpulses. Now as previously indicated, the storage unit is for use in asystem wherein successive elements of time represent successive numbercycles, with each cycle being divided into equal time periods, each ofwhich represents a number value. Thus, as indicated in Fig. 2, eachcycle may be divided into ten time periods with the first period in eachcycle representing a 9 value and the subsequent time periods in eachcycle representing 8, 7, 6, 5, 4, 3, 2, 1, and 0 values in the ordernamed. The synchronizing number impulse source is adapted to supply apositive voltage impulse once in 3 each number value period of everycycle as shown in Fig. 2.

The two screen grids llscg' of the control tube 11 shown in Fig. 1 areconnected together and through a series connected resistor 21 andinductor 22 to the +400 volts suppryune 13. In addition, the screengrids llscg are con nected through a capacitor 23 and a resistor 24 tothe grounded line 19. Another resistor 25 is connected from the junctionpoint between capacitor 23 and resistor 24 to a -250 volts supply line26. The screen grids llscg are originally at a voltage level ofapproximately +400 volts, but voltage variations at the screen grids aretrans mitted through capacitor 23 to the grid 27g of tube 27 which isbiased at approximately '50 volts.

The suppressor grid llsg of the control tube 11 is connected internallyto the cathode.

It, is apparent that if the clamping tube 20 becomes conductive, itcauses the potential impressed on the first control grid llbgl to dropapproximately to ground potential, i. e., line 19. This results in aCharging of the timing capacitor 18 with the plate thereof which isconnected to the first control grid 11g1 being negative. If the clampingtube 20 subsequently becomes non-conductive, the capacitor 18 isdischarged through resistors 12, 16 and 17 tjo gradually restore thefirst control grid llcgl to its original voltage level. The timeconstant of the discharge circuit, for reasons which will appear inconnection with the subsequent discussion of the operation of thestorage unit, is adjusted so that the first control grid llcgl reaches avoltage starting a flow of screen grid current approximately eightnumber value periods after the clamping tube 20 becomes non-conductiveand reaches its maximum value which is slightly more positive than thecathode as limited by the grid current, approximately nine number valueperiods after the clamping tube 20 becomes nonconductive.

The arrangement is such that when the first control grid 11'cg1 of tube11 is at the level of the grounded line 19 and the second control grid11cg2 is at its normal level between two number impulses, the flowofcathode current through control tube 11 is cut off with the voltage ofthe screen grid llscg at its original voltage level. This is thecondition illustrated in Fig. 2 at thebeginning of the sp'ace impulse inthe seven number value period of cycle X. The space impulse, as isexplained later, causes the clamping tube 20 to become non-conductivepermitting the first control grid ll'cgl to start upward. As the firstcontrol grid starts upward, each n'umber impulse on the second controlgrid, because of the interelectrode capacity, causes a small positivevoltage impulse on the screen grids llscg. When the first control gridllcgl becomes sufiiciently positive to allow some screen grid to cathodecurrent to flow, which occurs eight number value periods after theclamping tube 20 becomes nonco'nductive as shown in the nine numbervalue period in cycle Y, the screen gn'd voltage level starts to drop.In one additional number value period, i. e., the eight number valueperiod in cycle Y, the screen grid voltage drops from its original levelof approximately +250 volts to a level of about +100 volts where itremains, the first control grid llcgl having reached its maximum value.The number impulse occurring in the eight number value period producesonly a small impulse at the screen grid superimposed on the negativelysloping voltage as the plate transconductance is still small. When thenumber pulse occurs in the tenth period after the clamping tube 20becomes non-conductive, as shown in the seven number value period incycle Y, the first control grid llcgl has become sufficiently positivethat the number impulse causes the control tube to conduct and therebyproduce a negative voltage at its anode which is fed through thecapacitor 18 to the first control grid 11cg1 to cut oh the tube. Thisaction causes the screen grid voltage to rise sharply in a large impulseabove its original voltage level.

The large screen grid voltage impulse occurring exactly ten number valueperiods after the clamping tube 20 was rendered non-conductive isemployed to cause the clamp ing tube 20 to again become conductive. Toaccomplish this a triode tube 27 is provided as shown in Fig. l. Theanode of tube 27 is connected to +250 volts supply line 28 and its grid27g is connected to the junction of capacitor 23 and resistor 24. Thecathode 27k of tube 27 is connected through the anode and cathode oftriode tube 29 and a resistor 30 to 250 volts supply line 26. Thecathode 27k is also connected through a capacitor 31 to the anode of aninput triode tube 32. The anode 32a of tube 32 is connected through aresistor 33 to +250 volts supply line 28. The cathode 32a of tube 32 isconnected to ground line 19. The cathode 27k of tube 27 is alsoconnected directly to the grid of clamping control tube 34.

The tube 29 may be a triode. The grid of tube 29 is coupled through acapacitor 35 to a source of synchronous voltage impulses, designated asspace impulses. These space impulses are to be supplied as indicated inFig. 2, i. e., one space impulse in each number value period at a timein that period later than the number impulse. The grid of tube 29 inFig. l is also connected through a resistor 36 to the cathode of tube29. A capacitor 37 is connected between the cathode of tube 29 andground line 19.

The arrangement of tube 29 is such that said tube is normallynon-conductive but conducts an impulse of current each time a spaceimpulse is supplied to its gn'd. When the tube 29 is conductive itlowers the voltage level of the cathode 27k of tube 27 to a voltagewhich is only slightly more positive than the -50 volts supplied to grid27g of tube 27.

The input tube 32 is normally cut off so that its anode 32A is almost atthe level of the +250 volts supply line 28. This input tube 32 functionsas described herematter to cause a negative voltage impulse to appear atits anode when it is desired to store a number (or data) in the storageunit.

The clamping control tube 34 is illustrated in Fig. l as one-half of atype 12AT7 tube with its anode connected to the +250 volts line 28 andits cathode connected through resistor 38 to the 250 volts line 26. Thecathode of clamping control tube 34 is also connected to the grid of theclamping tube 20 so that the operation of the clamping tube depends onthe voltage level of the cathode of the clamping control tube. (Clampingcontrol tube 34 is used as a cathode follower to supply the gridpotential necessary to obtain good clamping action by clamping tube 20).

As may be seen in Fig. 2 the voltage impulses appearing at the screengrid llscg of control tube 11 are differentiated and applied to the grid27g of tube 27. The voltage bias provided through resistors 24 and 25keeps the grid 27g quite negative except when a large impulse appears atthe screen grid llscg of control tube 11 as occurs in the seven numbervalue period in cycle Y in Fig. 2. Since tube 29 becomes conductive oncein each number value period, the capacitor 31 is charged with a polarityas indicated in Fig. 1. The relative value of the bias voltage on thegrid 27g and the charge on the capacitor 31 results in tube 27 beingnormally cut off.

7 Preferably the arrangement is such that each space impulse causingtube 29 to conduct reduces the voltage level of the cathode 27k slightlywhich causes tube 27 to conduct a small amount of current which in turncauses the voltage level of the cathode 27k to rise slightly until thetube 27 is again cut ofi. Consequently the voltage level of the cathode27k is not exactly constant in between impulses at the screen grid llscgof control tube 11. In addition each of the small impulses at the screengrid llscg causes a small current flow through tube 27. However, thesevariations in the voltage level of the cathode 27k of tube 27 arerelatively small and have no-substantial eflect upon the overalloperation; For this reason, in the interestof clarity, these smallvariations are not shown in the curves ofFig. 2. It is suificient to saythat the voltage level of the cathode 27k andhence of the cathode oftube 34 are maintained sufliciently negative, except when a largeimpulse appears at the screen grid llscg of control tube '11, to causethe clamping tube 20 to remain non-conductive.

When a large voltage impulse appears at the screen grid llscg of controltube 11, exactly ten number value periods after the clamping tube 20last became nonconductive as in the seven number value period in cycle Y(shown in Fig. 2), the tube 27 becomes conductive to make the cathode27k and therefore the grid of the clamping control tube 34 morepositive. As a result clamping control tube 34 becomes more conductive.Also, clamping tube 29 again becomes conductive because of theconnection between the cathode of tube 34 and the grid of tube 29. Whenthe next subsequent space impulse causes tube 29 to become conductivethe cathode 27k is lowered to its original negative value, i. e.,capacitor 31 is recharged. When the cathode 27k is thus lowered, theclamping control tube 34 is cut oil to in turn cut off the clamping tube2%). With clamping tube 20 cut 03 discharging of the timing capacitor 18is again initiated. Thus the clamping tube becomes non-conductive at apredetermined instant in the number value period, that is, the instantwhen the space impulse is supplied, so that the timing of the delayaiforded by the discharge circuit of the timing capacitor 18 is alwaysinitiated at the same relative instant in 'the number value period.Consequently, if the clamping tube 20 has been operated originally in aselected number value period, the clamping tube will thereafter beoperated in the same number value I period in each successive cycle.

To store a number in the storage unit the input tube 32 is provided. Theinput tube 32 may be a triode. The grid 32g of tube 32 is coupledthrough a capacitor 39 (or any suitable coupling means) to a suitablesource of positive input impulses. An input impulse occurs once in eachnumber value period at a time within each number value period prior tothe beginning of the space impulse. The grid 32g is also connectedthrough a resistor 40 to the .250 volts supply line 26 and throughanother resistor 41 to a suitable bias voltage supply control designatedthe store command control. The store command control is arranged tosupply either of two voltagelevels through the resistor 41 and is shownfor purposes of schematic illustration only as a double throw switch 42having two positions designated store and no store. In the no storeposition of the command control the resistor 41 is eflectively connectedto 65 volts line 43 to maintain tube 32 non-conductive at all times. Inthe store position of the command control, the resistor 41 iseffectively connected to ground line 19 so that each positive inputimpulse supplied to the grid 32g, While the command control is in storeposition, causes a corre sponding negative impulse at the anode 32a oftube 32.

Idealized wave-forms of the voltages appearing at the grid 32g and theanode 32a of tube 32 are shown in Fig. 2. With the command control in nostore position, as in number value periods 9 and 6 through of cycle Xand all of cycle Y, the bias on the grid 32g prevents the input impulsesfrom causing corresponding impulses at the anode 32a. in the eightnumber value period of cycle X, the command control is also in no storeposition during the input impulse but is thereafter changed to storeposition so that the bias on grid 32g is made more positive and thepositive input impulse in the seven number value period of cycle Xcauses a corresponding negative impulse at the anode 32a to store avalue of 7 in the storage unit. After this impulse in the seven numbervalue period of cycle X, the command control again returns to the nostore position in the example shown. The command control may of coursebe any suitable control capable of changing the bias on the grid 32g oftube 32 at the proper time to permit a selected input impulse to bestored in the storage unit. (It will be appreciated that during normaloperation the store command control switch may be placed in the store"position during a complete cycle or cycles).

The voltage regulating unit enclosed by broken line 15 in Fig. 1maintains the level of the line 14 at approximately one-half of thevoltage level of the supply line 13 and is in eifect a comparing device.The regulator 15 includes two comparing tubes 44 and 45 which may be thetwo halves of a type 12AX7 twin triode tube. The anode of the firstcomparing tube 44 is connected to the +400 volts supply line 13 and itscathode is connected through a resistor 46 to ground line 19. The gridof the first comparing tube 44 is connected directly to line 14 andthrough a capacitor 47 to ground line 19. The grid of the firstcomparing tube 44 is also connected through the anode and cathode oftube 48 to ground line 19.

The anode of the second comparing tube 45 is connected through aresistor 49 to the +400 volts supply line 13. The cathode of tube 45 isconnected to the cathode of the first comparing tube 44. The grid of thesecond comparing tube 45 is connected to the midpoint, 50, of aresistive divider comprising a pair of resistors 51 and 52 connected inseries between the +400 volts supply line 13 and the grounded line 19.The resistors 51 and 52 each have the same resistance so that the gridof the second comparing tube 45 is at a voltage level halfway betweenthe voltage of supply line 13 and ground line 19. It is also evidentthat the grid of the first comparing tube 44 is at the voltage level ofthe line 14.

Another voltage divider is connected between the +400 volts supply line13 and the 250 volts supply line 26. This divider comprises a tube 53, apair of voltage regulator tubes 54 and 55 (such as VRl tubes) and aresistor 56. These elements are serially connected in the order recitedbetween the supply line 13 and the supply line 26. The grid of tube 53is connected to the anode of the second comparing tube 45. Consequently,any variation in the voltage of the anode of the second comparing tube45 causes a corresponding variation in the voltage across the resistor56 in the divider. The grid of the vacuum tube 48 is connected to apoint 57 on' the variable voltage divider intermediate the resistor 56and the voltage regulator tube 55. It is thus evident that the impedanceacross the anode and cathode of tube 48 varies in accordance withvariations in the voltage across the resistor 56.

As described hereinbefore the control tube 11 becomes conductive once ineach cycle. During conduction of control tube 11 the capacitor 47 in thevoltage regulating unit 15 is charged. Capacitor 47 thus serves tomaintain the voltage on line 14 more positive than ground line 19. Theactual voltage level of line 14 is then determined by the degree ofconductivity of the tube 48. The conductivity of tube 48 depends uponthe voltage across resistor 56 which in turn depends upon theconductivity of tube 53 as controlled by the voltage level of the anodeof the second comparing tube 45. Now the grid of the second comparingtube, it will be recalled, is at a voltage level halfway between that ofsupply line 13 and the grounded line 19 while the grid of the firstcomparing tube 44 is at the voltage level of line 14. If the level ofsupply line 13 should vary, a corresponding variation appears at thegrid of the second comparing tube 45 to vary the voltage level of theanode of that tube. Thus, if the voltage level of supply line 13 shoulddrop slightly, the grid of the second comparing tube 45 becomes slightlymore negative causing the anode of tube 45 to become more positive. As aresult, the tube 53 becomes more conductive causing an increase in thevoltage across resistor 56. The increase in voltage across resistor 56makes the grid of tube 48 more positive and the resulting increase inconductivity of tube 48 lowers the voltage level of supply line 14slightly to match the lowered voltage level of the grid of the secondcomparing tube 45.

If the voltage level of supply line 13 remains constant but the voltagelevel of the line 14 varies, the change in conductivity of the firstcomparing tube 44 changes the voltage level of the cathode of the secondcomparing tube 45 and results in a variation in the conductivity of thesecond comparing tube. This change in anode voltage of the secondcomparing tube 45 which in turn results in a variation in theconductivity of tubes 53 and 48 brings the voltage level of line 14 intoagreement with the voltage level of the grid of the second comparingtube 45.

By providing the voltage regulating unit 15 to maintain the ratio of thevoltage on line 14 to the voltage on line 13 at a substantially constantvalue the accuracy and reliability of the storage unit is greatlyincreased and the voltage on line 13 may be allowed to vary over widelimits. The duration in time of the interval between the time when theclamping tube 20 becomes non-cnductive and the time when the controltube 11 becomes conductive in response to a number impulse dependsprimarily upon the discharging of the timing capacitor 18 to raise thelevel of the first control grid llcgl above a critical value relative tothe level of the cathode of control tube 11, that is, the level of line14. The time required for the grid to rise to the critical voltagerelative to the cathode voltage depends upon the ratio between thevoltages on lines 14 and 13. If this ratio is held constant, the timebetween an input pulse and each successive corresponding output pulse isconstant.

To read out a value stored in the storage unit an output tube 58 isprovided. The anode of tube 53 is connected to the +250 volts supplyline 28. The cathode of tube 58 is connected through a resistor 59 tothe 250 volts supply line and an output terminal is connected to thecathode. Thus the output tube circuit is in efiect a cathode followercircuit.

The grid of tube 58 is connected to a point 60 intermediate a pair ofresistors 61 and 62 which are connected in series with each other in theorder named from the cathode of the clamping control tube 34 to the readout control. The read out control may be any suitable device forapplying either of two different voltages to the end of resistor 62which is remote from resistor 61. For purposes of illustration only theread out control is shown in Fig. l as a double throw switch 63. In oneposition of switch 63 the resistor 62 is connected to 65 volts supplyline 43. This position of switch 63 is labelled no road. In the otherposition of switch 63 which is labelled read the resistor 62 isconnected to ground line 19. From explanations given hereinbefore itwill be recalled that the clamping control tube 34 becomes conductive atthe beginning of the number impulse in the number value periodcorresponding to the stored number (i. e., value) in each cycle andbecomes non-conductive at the beginning of the subsequent space impulsein that same number value period. Each time the clamping control tube 34becomes conductive, a positive voltage impulse appears at its cathodeand is transferred through the resistor 61 to the grid of the outputtube 58. When the read out control is in the no read position, thevoltage level at the grid of the output tube 58 is low as compared withthe voltage level at the grid of the output tube 58 when the read outcontrol is in the read position. It is to be appreciated that a positiveimpulse impressed on the grid of tube 58 when said grid is at the higherof the two voltage levels will result in tube 58 being renderedconductive and an impulse appearing at the output terminal. The outputimpulse will occur during the number value period corresponding to thestored number. The above condition will exist and the above sequence ofoperation take place whenever the readout control is in the readposition and a value is stored within the novel storage unit.

While the operations of various portions of the storage unit have beenset forth in connection with the detailed description of those portions,it is believed that a ail) more comprehensive understanding of theoperation of the storage unit may be obtained by disclosing a specificexample with reference to both Fig. 1 and Fig. 2. Let it be assumed thatthe storage unit is in operation and has a O stored therein. Let itfurther be assumed that when the storage unit reaches cycle X it isdesired to store a 7 therein. Now when cycle X is reached we find, asshown in Fig. 2 that number impulses are being supplied to the secondcontrol grid 11cg2 once in each number value period. A space impulse isbeing delivered to the grid of the tube 29 in Fig. 1 once in each numbervalue period at a time in that period subsequent to the number impulseas shown in Fig. 2. An input impulse is delivered to the grid 32g of theinput tube 32 in Fig. 1 once in each number value period at a time ineach such period prior to the number impulse. The command control i inthe no store position at this time so that the level of the inputimpulses on grid 32g remains below the critical value of the tube asreported by the broken line 64 in Fig. 2.

With a 0 stored in the unit the first control grid llcgl of the controltube 11 is at the beginning of cycle X gradually rising in voltage fromthe low negative value assumed in the 0 number value period of thepreceding cycle when the clamping tube 20 was conductive. The gradualrise in voltage of the first control grid 11cg1 is due to thedischarging of the timing capacitor 18. However, in the beginning ofcycle X the voltage of the first control grid llcgl is stillconsiderably below the critical value as reported by the broken line 65in Fig. 2.

When the first control grid 11cg1 is at the voltage indi-' cated at thebeginning of cycle X, the voltage of the screen grid llscg of thecontrol tube 11 is at a relatively high level. The tube 27 isnon-conductive and the clamping control tube 34 and the clamping tube 20are also non-conductive.

In the nine and eight number value periods of cycle X the input impulsesimpressed on grid 32g do not result in the potential rising above thecritical value thus the input tube 32 is non-conductive. This conditionexists because the command controlis in the no store position. Thenumber impulses in the nine and eight number value periods do causevariations in the voltage of the screen grid llscg, but the resultingvoltage variations of the grid 27g of tube 27 are insufficient to causemore than a slight variation in the voltage level of the cathode 27k.For clarity these variations of the voltage level of cathode 27k areomitted in the idealized waveforms of Fig. 2. Consequently the clampingcontrol tube 34 and the clamping tube 20 remain non-conductive in thenine and eight number value periods.

In the eight number value period after the input impulse in that periodha been delivered the store command is changed from the no store to thestore position raising the voltage level of the grid 32g of the inputtube 32. Then at the beginning of the seven number value period of cycleX the corresponding input impulse raises the voltage of the grid 32gabove the critical value causing the input tube 32 to pass a currentimpulse. This results in a negative voltage impulse at the anode 32aofthe input tube as is seen in Fig. 2. The negative impulse at the anode32a in Fig. 1 tends to cause a similar negative impulse (not shown inFig. 2) at the cathode 27k of tube 27. However, the grid 27g ismaintained at approximately 50 volts, thus the flow of cathode currentfrom cathode 27k prevents the potential at this point from fallingsignificantly below -50 volts and further charging capacitor 31. At thetermination of the input impulse applied to grid 32g the plate 32a oftube 32 tends to rise again to +250 volts and this rise in potential istransmitted through capacitor 31 to cathode 27k causing the potential atthat point to rise to approximately ground level. When the cathode 27kis thus raised, the grid of clamping control tube 34 is likewise raisedto cause the clamping control tube to become more con- 9 ductive, whichin turn causes the clamping tube 20 to become conductive. When theclamping tube 20 becomes conductive the voltage of the first controlgrid 11cg1 of the control tube 11 is dropped almost to the voltage levelof the grounded line 19. The cathode 27k of tube 27 remains at thevoltage level of ground and the clamping control tube 34 and theclamping tube 20 remain conductive until the beginning of the spaceimpulse in this same seven number value period of cycle X. While theclamping tube 20 is conductive the timing capacitor 18 is charged byvirtue of the circuit extending from the +400 volts supply line 13through the resistor 12, the timing capacitor 13 and the clamping tube20 to ground line 19.

The space impulse of the seven number value period of cycle X isdelivered to the grid of tube 29 causing that tube to become conductiveto lower the cathode 27k of tube 27 to its original (negative) voltagelevel and held there due to capacitor 31 being re-charged. With cathode27k at this negative voltage level, the clamping control tube 34 and theclamping tube 20 become non-conductive.

While the clamping control tube was conductive in the seven number valueperiod of cycle X, an impulse appeared at the output terminal. However,since the read out control was in the no read position, this outputimpulse is at a relatively low voltage level.

When the clamping tube 20 becomes non-conductive, the timing capacitor18 begins to discharge through resistors 12, 16 and 17 at apredetermined rate. Consequently, the voltage level of the first controlgrid 11cg1 gradually rises through the next several number valueperiods. So long as the voltage of the first control grid llcgl remainsbelow the critical value represented by line 65 the number impulsescause only small impulses at the screen grid llscg which areinsufficient to cause tube 27 to become conductive.

The rate of discharge of the timing capacitor 13 is such thatapproximately eight number value periods after the clamping tube 20becomes non-conductive (i. e., eight number value periods after theseven number value period of cycle X), the first control grid llcglbecomes sufficiently positive that a substantial screen grid currentbegins to flow. This occurs in the nine number value period of the nextcycle which is labelled cycle Y in Fig. 2. Consequently, the voltage ofthe screen grid llscg begins to drop rapidly. When the number impulseoccurs in the eight number value period of cycle Y the screen gridvoltage is still declining rapidly. Since the transconductance of thecontrol tube 11 is still small and the voltage of grid 27g of tube 27 islowered slightly because of the differentiation of the dropping screengrid voltage, the resulting impulse in the screen grid voltage is noteffective to cause tube 27 to conduct. Toward the end of the eightnumber value period in cycle Y the first control gn'd 11cg1 of thecontrol tube 11 is sufficiently positive that the screen grid voltage islevelled and is no longer dropping. Then the number impulse in the sevennumber value period of cycle Y causes the control tube 11 to conductthrough its anode-cathode circuit. This results in a negative voltageimpulse at the anode of the control tube 11, which impulse istransferred through the capacitor 18 to the first control grid 11cg1.This causes a very large positive impulse to appear at the screen grid11scg which is transferred to the grid 27g of tube 27 to cause that tubeto conduct momentarily.

When tube 27 becomes conductive in the seven number value period ofcycle Y, its cathode 27k becomes more positive rising to the level ofground line 19 where it is maintained until the beginning of thesubsequent space impulse in the same number value period. While thecathode 27k is at this higher level the clamping control tube 34 and theclamping tube are conductive. When the clamping tube 20 becomesconductive the timing capacitor 18 is again charged to drop the voltageof the first control grid 11cg1 of control tube 11 to its lowest value.When the clamping tube 20 becomes non conductive the capacitor 18 againbegins to discharge and the voltage of the first control grid 11cg1begins to rise.

It is then obvious that until another number is stored through theoperation of the command control, the clamping tube 20 will becomeconductive at the beginning of the number impulse in each seven numbervalue period of each succeeding cycle. Whenever a difierent number is tobe stored in the storage unit the command control is operated to permitthe corresponding input impulse to render the tube 32 conductive in thecorresponding number value period. Such action will remove the storednumber seven from the unit and will replace it with the new number.

When it is desired to read out the number which is stored in the storageunit, the read out control is moved into the read position at thebeginning of a cycle. For example, assume that at the beginning of cycleY this new position (i. e., read-out position) of the read out controlraises the level of the output terminal as indicated in Fig. 2.

It is to be particularly noted that the clamping tube 20 is alwaysrendered conductive as a result of a number impulse, and is renderednon-conductive as a result of the subsequent space impulse in the samenumber value period of the same cycle. Consequently, discharging of thetiming capacitor 18 is initiated synchronously and is endedsynchronously. In addition, the interval between initiation and endingof the discharging period of the timing capacitor 18 is maintainedaccurate by maintaining the voltage level of line 14 substantiallyconstant. Thus the first control grid llcgl is arranged to operatebetween two fixed voltage levels.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwith out departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. A storage device for use in storing for an indefinite period datarepresented by a voltage impulse comprising, an electron dischargedevice including a cathode, an anode, a first control electrode, asecond control electrode and a screen electrode, a resistance-capacitornetwork coupling said anode and said first control electrode with afirst source of positive potential, voltage regulator means formaintaining said cathode at a substantially constant second positivepotential, synchronous means for periodically impressing a positivepotential on said second control electrode, clamp circuit means couplingsaid first control grid with ground potential, means coupling saidscreen electrode and said clamp circuit means whereby the storage deviceis capable of accepting an input impulse and periodically regeneratingan output impulse.

2. A storage device as claimed in claim 1 wherein the means couplingsaid screen electrode and said clamp circuit means includes a clampingtube, a clamping control tube and an additional tube capacitivelycoupled to said screen electrode.

3. A storage device for use in storing for an indefinite period datarepresented by an electrical impulse comprising, an electron dischargedevice including a cathode, an anode, a first control electrode, asecond control electrode and a screen electrode, a resistance-capacitornetwork coupling said anode and said first control electrode with afirst source of positive potential and a clamping tube, voltageregulator means for maintaining said cathode at a substantially constantsecond positive potential, synchronous means for periodically impressinga positive potential on said second control electrode, a clampingcontrol tube for controlling said clamping tube, a

I 1 1 first triode capacitively coupled to said screen electrode andconnected to said clamping control tube, means responsive to anelectrical input impulse to'be stored for energizing said clampingcontrol tube and said clamping tube and thereby charging the capacitorof said resistancecapacitor network, and cyclic means operative after anelectrical input impulse has been stored for periodically causing saidclamping control tube and said clamping tube to be conductive and chargesaid capacitor of said resistance-capacitor network and thereby generatean electrical output impulse.

4. A storage device as claimed in claim 3 further characterized in thatsaid cyclic means includes a second triode coupled to said first triodeand said clamping control tube, and second synchronous means forperiodically rendering said second triode conductive 5. A storage devicefor use in storing for an indefinite period data represented by anelectrical impulse comprising, an electron discharge device including acathode, an anode, a first control electrode, a second control electrodeand a screen electrode, a resistance-capacitor network coupling saidanode and said first control electrode with a first source of positivepotential and a clamping tube, means for maintaining said cathode at asecond positive potential which is a fixed percentage of the potentialof said first source of positive potential, synchronous means forperiodically impressing a positive potential on said second controlelectrode, a clamping control tube for controlling said clamping tube, afirst triode capacitively coupled to said screen electrode and connectedto said clamping control tube, means responsive to an electrical inputimpulse to be stored for energizing said clamping control tube andthereby charging the capacitor of said resistance-capacitor network, andcyclic means I operative after an electrical input impulse has beenstored for periodically causing said clamping control tube and saidclamping tube to be conductive and charge said capacitor of saidresistance-capacitor networkand thereby generate an electrical outputimpulse.

6. A delay circuit for use in delaying an electrical impulse for a fixedinterval of time, or any positive integer multiple of said fixedinterval of time comprising, an electron discharge device including acathode, an anode, a first control electrode, a second control electrodeand a screen electrode, a resistance-capacitor network coupling saidanode and said first control electrode with a first source of positivepotential and a clamping tube, means connecting said cathode with asecond source of positive potential, synchronous means for periodicallyimpressing a positive potential on said second control electrode, aclamping control tube for controlling said clamping tube, a first triodecapacitively coupled to said screen electrode and connected to saidclamping control tube, means responsive to an electrical input impulseto be delayed for energizing said clamping control tube and saidclamping tube and thereby charging the capacitor of saidresistance-capacitor network, and additional repetitive means forperiodically effecting the generation of an electrical output impulse.

References Cited in the file of this patent UNITED STATES PATENTS2,482,973 Gordon Sept. 27, 1949 2,584,882 Johnson Feb. 5, 1952 2,594,104Washburn Apr. 22, 1952 2,675,469 Harker et al Apr. 13, 1954

